Thieves broke into the Ancient Olympia Museum on Friday morning and stole between 60 and 70 artefacts, police said.
According to authorities, two robbers wearing hoods used hammers to smash their way into the museum at about 7.30 a.m. They tied and gagged the one female employee that was on duty and then stole the ancient relics.
Archaeological experts are assessing the damage and the number of items that have been stolen.
The museum, located next to the site where the Ancient Olympics were held, contains numerous valuable artefacts.
Skai TV reported that Culture Minister Pavlous Geroulanos has tendered his resignation.